The long range goal of this research is to increase the efficacy of topical floride therapy of human enamel. Incorporation of fluoride in enamel from systemic ingestion during tooth formation is in the form of fluorhydroxyapatite and is caries preventive. Certain formulations of fluoride, phosphate and surface active agents have been shown to accelerate formation of firmly (presumably apatitically) bound fluoride in enamel from topical application in vitro. The proposed work includes further development of a liquid self-gelling formulation of tetraethoxysilane and an aqueous fluoride solution which gels in situ after application to the teeth thus prolonging the contact time between fluoride vehicle and tooth surface. Specifically, it is proposed (1) to assess in vitro how to maximize formation of firmly bound fluoride in enamel by incorporation of specific surface active agents in the system and (2) to study in rodents the caries inhibitive effect of such self-gelling compositions and of solutions of fluoride, phosphate and surface active agents. The proposed research will result in formulations which may be clinically tested for topical application to the teeth or for use in dentifraces and mouthwashes. The formulations will have the protential to be more effective than those currently in use with the same fluoride concentration or equally effective, but containing less fluoride.